In many instances it is desirable or necessary to regularly monitor the concentration of particular constituents in a fluid. A number of systems are available that analyze the constituents of bodily fluids such as blood, urine and saliva. Examples of such systems conveniently monitor the level of particular medically-significant fluid constituents, such as, for example, cholesterol, ketones, vitamins, proteins, and various metabolites or blood sugars, such as glucose. Diagnosis and management of patients suffering from diabetes mellitus, a disorder of the pancreas where insufficient production of insulin prevents normal regulation of blood sugar levels, requires carefully monitoring of blood glucose levels on a daily basis.
In vivo analyte monitoring systems include an in vivo positioned analyte sensor. At least a portion of the sensor is positioned beneath the skin surface of a user to contact bodily fluid (e.g., blood or interstitial fluid (ISF)) to monitor one or more analytes in the fluid over a period of time, and analyte monitoring is done continuously over a period of time. This is also referred to as continuous analyte monitoring in that the sensor remains positioned in the user for a continuous period of time to automatically sense an analyte. Other forms of testing include in vitro testing (also known as ex-vivo)—e.g., by withdrawing blood from a patient and applying the blood to an ex vivo test strip for insertion into a glucose meter.
In continuous analyte monitoring, trends in the rate-of-change of analyte measurements, also referred to herein as “analyte trends”, are often useful to the user. For example, in addition to knowing analyte measurement levels, patients may also find analyte trends to be useful information in determining the necessity of treatment and its timing. An example of continuous analyte monitoring is continuous glucose monitoring (CGM).
Accordingly, there is a need for accurate and precise rate of change information.